The following proposal outlines a new methodology for the chemical senses and tests a specific hypothesis about taste bud function. We propose to apply highly-sensitive electrochemical microsensors to study neurotransmitters released by synapses in taste buds of mice and rats. Our hypothesis is that certain taste cells release serotonin as a neurotransmitter. [unreadable] [unreadable] To date, no neurotransmitter has been unambiguously identified and its release detected in taste buds. Electrochemical microsensors may accomplish this. This methodology utilizes small carbon fiber probes that measure the release of certain neurotransmitters, especially biogenic amines such as serotonin, dopamine and norepinephrine. Electrochemical microsensors using carbon fiber probes are highly sensitive--the amount of transmitter released by an individual synaptic vesicle can be reliably detected. This technique has been used for many years in investigations of central nervous system synapses and transmitter release in tissue cultures. Our pilot studies in rats suggest that electrochemical microsensors can also be applied to investigate synapses in taste buds and to monitor real-time release of serotonin. We will construct and optimize carbon fiber electrodes (CFEs) suitable for recording from taste buds. We will develop appropriate preparations of lingual tissues for recording transmitter release from taste bud cells in mice and rats. [unreadable] [unreadable] We will identify whether serotonin or some other biogenic amine is released by stimulating taste buds. We will test whether chemical or mechanical (or both) stimuli evoke serotonin and will also investigate other possible forms of stimulation (e.g. hyper- and hypoosmotic shock). [unreadable] [unreadable] The results will provide information about taste neurotransmitters and will shed light on the enigmatic role of the serotonergic Merkel-like cells found in taste buds. If these cells turn out to be mechanoreceptors, the results may explain how taste buds detect food texture. This will greatly further our understanding of food selection and diet. [unreadable] [unreadable]